Method, system and model for indirect bonding

ABSTRACT

A physical model of at least a portion of a patient&#39;s dentition has model dental surfaces corresponding to real dental surfaces of the patient&#39;s dentition. The physical model includes one or more targets, each configured for facilitating placement of an  5  orthodontic appliance on the model at a desired location. The targets lack mechanical stops that are outwardly protruding from the original model dental surfaces. Also provided are a method of manufacturing a physical model for use in indirect bonding procedures, a method for indirect bonding for use in an orthodontic procedure, a method for providing an indirect bonding transfer tray for use in an orthodontic procedure, and a  10  system for providing a physical model for use in indirect bonding orthodontic procedures.

CROSS-REFERENCE

This application is a continuation application of U.S. patentapplication Ser. No. 12/656,960, filed Feb. 22, 2010, which claimsbenefit under 35 U.S.C. 119(e) of U.S. Provisional Patent ApplicationNo. 61/202,387, filed Feb. 24, 2009, the contents of each of which arehereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

This invention relates to dental procedures, more particularly toorthodontic procedures, more particularly to methods, systems andaccessories including models and transfer trays used in such procedures,and specially relating to indirect bonding procedures.

BACKGROUND OF THE INVENTION

The branch of dentistry dealing with teeth irregularities and theircorrections, such as by means of braces, is known as Orthodontics. Theprimary purpose of orthodontic treatment is to alter the position andreorient an individual's teeth so as to modify or improve theirfunction. Teeth may also be reoriented mainly for cosmetic reasons.

In orthodontic treatment, as currently practiced, it is often necessaryto affix various orthodontic appliances to the surfaces of a patient'steeth. The location of the orthodontic appliance on the tooth as well asits orientation is a critical factor in determining the direction ofmovement of the teeth during the treatment, and accurate placement mayensure that the teeth are aligned with a single bracket bondingtreatment. Conversely, less accurate placement of orthodontic appliancesmay require repeated treatments, including repeated bonding and wirebending procedures until the final alignment is achieved.

Once the position of the orthodontic appliances has been decided upon,it is thus critical that a good bond is established between theorthodontic appliances and the teeth at that position. Orthodonticappliances affixed to teeth surfaces serve to support wires andtensioning springs to exert moments of force acting to move the teethsubjected to these forces to a degree and in a direction causing theteeth to assume a desired posture in the dental arch.

In current orthodontic practice, the orthodontist decides on a generalscheme of placing the orthodontic appliances on the teeth and thenattaches each of them to the surface of a tooth, in an exact locationand orientation previously decided. Preparatory to an orthodontictreatment, the orthodontist typically prepares a plaster model of theteeth of the treated individual and on the basis of such model, and thegeneral scheme of placement of the orthodontic appliances can bedecided.

A typical treatment plan includes, among other factors, the desiredposition of each of the force-inducing orthodontic implements on theteeth. The placement of the orthodontic appliances on the teethdetermines the outcome of the above-mentioned movements, e.g. the degreeand direction of the teeth movements. Any deviation from the plannedposition of the orthodontic appliances affects the outcome of thetreatment. Thus, during the process of placing the orthodonticappliances on the teeth, much effort is made to ensure the accuratepositioning of the orthodontic appliances in accordance with theirdesired position as determined by the treatment plan, and to ensure thatthe orthodontic appliances are properly bonded to the teeth at thesepositions.

The orthodontic appliances are typically placed on the buccal surface ofthe teeth, though at times, it is desired both from a treatmentperspective as well as for reasons of external appearance of theindividual, to place the orthodontic appliances on the lingual surfaceof the teeth.

One form of positioning brackets is known as indirect bonding, and istraditionally based on forming a tray of a thermoplastic material, orany other suitable material, over a physical model of the teeth on whichthe brackets have been positioned using a relatively weak adhesive, forexample as described in U.S. Pat. No. 3,738,005. The brackets may bepositioned onto the model in any one of a number of ways, for example asdisclosed in U.S. Pat. No. 4,812,118. The tray thus comprises a negativeimpression of the teeth model, which is very close-fitting with respectthereto, and also has the brackets embedded in position in the tray intheir correct positions with respect to the model. The tray can then beremoved from the model, taking with it the brackets in the correctrelative positions with respect to the negative impression. The tray isthen transferred to the intraoral cavity of the patient, and whenproperly fitted over the appropriate arch, presents the brackets inostensibly the correct positions vis-à-vis the teeth. It is thenattempted to bond the brackets simultaneously onto the teeth, and thetray may then be removed, leaving the brackets in place.

This method is commonly practiced, and can be used for both buccal andlingual brackets. Most of the preparatory work is done by a technicianrather than the dentist, and the technique results in a shorterinstallation time than when the brackets are installed manually one at atime, but the technician needs to have a supply of brackets readilyavailable. This method also requires all the teeth to be dry andpre-etched, before bonding begins.

Some patent publications of general background interest include: U.S.Pat. No. 5,971,754; U.S. Pat. No. 4,360,341; U.S. Pat. No. 6,123,544;U.S. Pat. No. 4,501,554, US 2005/0244790; US 2004/0253562; US2004/0229185.

SUMMARY OF THE INVENTION

In this specification, we shall only refer to brackets as particularexamples of the orthodontic appliance (also interchangeably referred toas orthodontic element or component), to be anchored on a tooth'ssurface, but it is to be understood that this is only by way of example,and the invention applies to all other types of orthodontics appliances,mutatis mutandis, such as for example tubes, springs and otherappliances that are configured for being affixed to a dental surface forproviding an orthodontic treatment.

According to a first aspect of the invention, there is provided aphysical model of at least a portion of a patient's dentition, saidmodel comprising model dental surfaces corresponding to real dentalsurfaces of the patient's dentition, said physical model furthercomprising at least one target configured for facilitating placement ofan orthodontic appliance on said model at a desired location, andwherein the or each said target lacks mechanical stops that areoutwardly protruding from the said model dental surfaces.

More specifically, the or each said target lacks mechanical stops thatare outwardly protruding from the said model dental surfaces and thatare configured for locating the orthodontic appliance by abutment on thestops. By model dental surfaces is meant dental surfaces of real teeththat are replicated in the physical model.

According to at least some embodiments of the invention, the or eachsaid target comprises physical and/or optical clues correlated to arespective said desired location such as to enable the respective saidorthodontic appliance to be targeted onto the respective said location.

In at least some embodiments, at least one or the said target comprisesa recess (interchangeably referred to herein also as a cavity and/orindentation) formed into, i.e., projecting into said model dentalsurface, said recess having at least one recess edge complementary to anappliance edge of a said orthodontic appliance the recess edge beingconfigured for enabling the appliance to be received in said recess andlocated therein by abutment between said appliance edge and saidrespective recess edge.

In a variation of this embodiment, at least one or the said targetcomprises a recess formed into said model dental surface, said recesshaving at least two recess edges complementary to two appliance edges ofa said orthodontic appliance to be received in said recess and locatedtherein by abutment between said appliance edges and said respectiverecess edges.

In another variation of this embodiment, at least one or the said targetcomprises a recess formed into said model dental surface, said recesshaving at least three recess edges complementary to three applianceedges of a said orthodontic appliance to be received in said recess andlocated therein by abutment between said appliance edges and saidrespective recess edges.

In another variation of this embodiment, at least one or the said targetcomprises a recess formed into said model dental surface, said recesshaving a plurality of recess edges complementary to the appliance edgesof a said orthodontic appliance to be received in said recess andlocated therein by abutment between said appliance edges and saidrespective recess edges. For example, the appliance may have four edges,and the recess also has four complementary edges.

In another embodiment, at least one or the said target comprises aphysical marking or visual marking formed on said model dental surface,said marking providing sufficient visual clues to enable saidorthodontic appliance to be located at the desired location on the modeldental surface. For example, the physical marking may comprise a mark orsymbol indented, engraved or otherwise formed projecting into said modeldental surface (for example as a mild depression) having sufficientvisual targeting information to enable a user to navigate a respectivesaid orthodontic appliance and targeted the same onto a desired locationon said model. In another example, the visual marking may comprise amark or symbol having an optical characteristic different from anoptical characteristic of a remainder of said model dental surface notcomprising said target, and having sufficient visual targetinginformation to enable a respective said orthodontic appliance to betargeted to a desired location on said model; the optical characteristicmay include, for example, at least one of color and contrast. Themarkings may be inscribed, printed or otherwise formed in the model, andhelp to visually align the orthodontic appliance at the desiredposition, without the need for physical stops to keep it in place.

The targets, in particular the recesses and/or markings may be made byCNC machining the physical model, for example, during manufacture of themodel or after manufacture of the model. Alternatively, other materialremoval manufacturing processes may be used for manufacturing the modeland targets. Alternatively, other methods may be used for manufacturingthe model and targets, for example rapid prototyping techniques. Opticalmarkings may be provided on the physical model by means of computercontrolled printing, drawing or other methods that leave a mark orsymbol on the model.

The physical marking or visual marking may be configured for enabling adatum mark on said appliance to be aligned therewith such as to locatethe appliance at the desired position on the model.

In any particular application of the invention, a plurality of targetsmay be provided on a corresponding plurality of model teeth of aphysical model, according to the requirements of a treatment plan, andthe targets may include any combination or permutation of differenttypes of targets—for example a mix between targets that provide arecessed mechanical stop for physically anchoring the respectiveappliance on the tooth model (the same type of mechanical stop, ordifferent types of mechanical stops), and targets in the form of opticalmarkings that only provide an optical guide (but no anchoring stops) toenable the appliance to be navigated and targeted into the desired place(the same or different types of optical markings). Alternatively, thesame type of target may be provided throughout the model. In at leastsome applications, at least one target may include both a recessedmechanical stop and an optical marking for targeting.

According to a second aspect of the invention, there is provided amethod of manufacturing a physical model for use in indirect bondingprocedures, comprising:

(a) providing a physical model of at least a portion of the intra oralcavity of a patient;

(b) determining desired positions of orthodontic appliances with respectto said intra oral cavity to enable an orthodontic procedure to becarried out;

(c) providing at least one target on the physical model, the or eachsaid target being configured for facilitating placement of saidorthodontic appliance on said physical model at a desired location, andwherein the or each said target lacks mechanical stops that areoutwardly protruding from the said model dental surfaces.

The positions in step (b) may be determined with respect to a virtualmodel corresponding to the physical model of step (a).

Step (c) may be carried out by means of a computer controlledmanufacturing process, including, for example, at least one of a CNCmachining process and a rapid prototyping manufacturing process.

In at least some embodiments, step (c) is performed concurrently whilemanufacturing the physical model in step (a).

The physical model may contain one or more characteristic and featuresof the physical model as per the first aspect of the invention, mutatismutandis.

According to a third aspect of the invention there is provided a methodfor indirect bonding for use in an orthodontic procedure, comprising:

(a) providing a physical model of at least a part the intra oral cavityof a patient, said physical model comprising at least one target, the oreach said target being configured for facilitating placement of saidorthodontic appliance on said physical model at a desired location forenabling said orthodontic procedure, and wherein the or each said targetlacks mechanical stops that are outwardly protruding from the said modeldental surfaces;

(b) using the targets, locating the orthodontic appliances at respectivesaid desired positions on said physical model;

(c) providing a transfer tray over said physical model such as to anchorsaid orthodontic appliances within said transfer tray;

(d) transferring the orthodontic appliances to the real intra-oralcavity of the patient.

The physical model may contain one or more characteristic and featuresof the physical model as per the first aspect of the invention.

According to a fourth aspect of the invention, there is provided amethod for providing an indirect bonding transfer tray for use in anorthodontic procedure, comprising:

(a) providing a physical model of at least a part the intra oral cavityof a patient, said physical model comprising at least one target, the oreach said target being configured for facilitating placement of saidorthodontic appliance on said physical model at a desired location forenabling said orthodontic procedure, and wherein the or each said targetlacks mechanical stops that are outwardly protruding from the said modeldental surfaces;

(b) using the targets, locating the orthodontic appliances at respectivesaid desired positions on said physical model;

(c) producing a transfer tray over said physical model such as to anchorsaid orthodontic appliances within said transfer tray;

(d) removing the transfer tray, with the orthodontic appliances in situtherein, from the physical model.

The physical model according to the fourth aspect of the invention mayhave one or more characteristic and features of the physical model asper the first aspect of the invention, mutatis mutandis.

According to a fifth aspect of the invention, there is provided a systemfor providing a physical model for use in indirect bonding orthodonticprocedures, comprising a computer controlled manufacturing centerconfigured for producing, on a physical model of at least part of theintra-oral cavity of a patient, at least one target, the or each saidtarget being configured for facilitating placement of an orthodonticappliance on said physical model at a desired location for enabling anorthodontic procedure to be carried out on the patient, and wherein theor each said target lacks mechanical stops that are outwardly protrudingfrom the said model dental surfaces.

The physical model according to the fifth aspect of the invention mayhave one or more characteristic and features of the physical model asper the first aspect of the invention, mutatis mutandis.

Thus, according to at least some aspects of the invention, a physicalmodel of at least a portion of a patient's dentition has model dentalsurfaces corresponding to real dental surfaces of the patient'sdentition. The physical model includes one or more targets, eachconfigured for facilitating placement of an orthodontic appliance on themodel at a desired location. The targets lack mechanical stops that areoutwardly protruding from the original model dental surfaces. Alsoprovided are a method of manufacturing a physical model for use inindirect bonding procedures, a method for indirect bonding for use in anorthodontic procedure, a method for providing an indirect bondingtransfer tray for use in an orthodontic procedure, and a system forproviding a physical model for use in indirect bonding orthodonticprocedures.

One feature of at least some embodiments and aspects of the invention isthat the 5 targets may be retrofittably provided in existing physicalmodels, as the targets are marked on the model or recesses provided intothe surface of the model.

Another feature of at least some embodiments and aspects of theinvention is that the physical model can be easily repaired if damaged,or if a different position is required. For example, an existing recesscan be filled in and re-machined, or an existing marking can be erasedor covered over and redrawn.

Another feature of at least some embodiments and aspects of theinvention is that the exact location in all degrees of freedom of anorthodontic appliance on a real tooth can be exactly repeated in a toothmodel, by providing where necessary buffer layer between the model andthe appliance.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carriedout in practice, embodiments will now be described, by way ofnon-limiting example only, with reference to the accompanying drawings,in which:

FIG. 1 is an isometric exploded view of a physical model and transfertray according to embodiments of the invention; FIG. 1 a shows across-sectional view of the model and tray of FIG. 1, taken at aposition comprising an orthodontic appliance; FIG. 1 b shows across-sectional view of the real tooth corresponding to the model ofFIG. 1 b and comprising an orthodontic appliance, with the tray beingremoved.

FIGS. 2 a to 2 f show various views of a tooth model portion of thephysical model of FIG. 1, including a target according to a firstembodiment of the invention: FIGS. 2 a, 2 b illustrate the target on thetooth model in isometric and cross-sectional view, respectively; FIGS. 2c, 2 d illustrate the orthodontic appliance in situ on the target on thetooth model in isometric and cross-sectional view, respectively; FIGS. 2e, 2 f illustrate in side view, a variation of the embodiment of FIGS. 2a to 2 d, the orthodontic appliance mounted to the tooth model via abuffer layer and the orthodontic appliance mounted to the real toothwithout the buffer, respectively.

FIGS. 3 a to 3 c show in a variation of the embodiment of FIGS. 2 a to 2f; FIG. 3 a illustrates a cross-section of the tooth model showing theshape of the recess; FIG. 3 b illustrates a cross-section of the toothmodel showing the orthodontic appliance mounted in the recess; FIG. 3 cillustrates a side view of the real tooth showing the correspondingchange in angular position of the orthodontic appliance relative to itsposition in FIG. 3 b.

FIGS. 4 a to 4 g show various views of another variation of theembodiment of FIGS. 2 a to 2 f: FIGS. 4 a, 4 b illustrate the target onthe tooth model in isometric and cross-sectional view, respectively;FIGS. 4 c, 4 d illustrate the orthodontic appliance in situ on thetarget on the tooth model in isometric and cross-sectional view,respectively; FIGS. 4 e, 4 f illustrate in side view the orthodonticappliance captured in the transfer tray and being removed from the toothmodel, and the orthodontic appliance mounted to the real tooth,respectively; FIG. 4 g illustrates in side view, a variation of theembodiment of FIGS. 4 a to 4 f, in which the orthodontic appliance ismounted to the tooth model via a buffer layer.

FIGS. 5 a to 5 d show various views of another variation of theembodiment of FIGS. 2 a to 2 f: FIGS. 5 a, 5 b illustrate the target onthe tooth model in isometric and cross-sectional view, respectively;FIGS. 5 c, 5 d illustrate the orthodontic appliance in situ on thetarget on the tooth model in isometric and cross-sectional view,respectively.

FIGS. 6 a to 6 h show various views of a second embodiment of theinvention and variations thereof: FIGS. 6 a, 6 b illustrate the targeton the tooth model in isometric and cross-sectional view, respectively;FIGS. 6 c, 6 d illustrate variations of the embodiment of FIGS. 6 a and6 b; FIGS. 6 e and 6 f show yet another variation of the embodiment ofFIGS. 6 a and 6 b; FIGS. 6 g and 6 h illustrate examples ofcross-sections of the embodiments of the targeting marks of FIGS. 6 a to6 f.

FIG. 7 illustrates general steps of a method for manufacturing the toothmodel of FIG. 1 according to an embodiment of the invention.

FIG. 8 illustrates general steps of another method for manufacturing thetooth model of FIG. 1 according to an embodiment of the invention.

FIGS. 9 a to 9 d show various views of a third embodiment of theinvention: FIGS. 9 a, 9 b illustrate the target on the tooth model inisometric and cross-sectional view, respectively; FIGS. 9 c, 9 dillustrate the orthodontic appliance in situ on the target on the toothmodel in isometric and cross-sectional view, respectively.

FIGS. 10 a to 10 d show various views of another variation of theembodiment of FIGS. 9 a to 9 d: FIGS. 10 a, 10 b illustrate the targeton the tooth model in isometric and cross-sectional view, respectively;FIGS. 10 c, 10 d illustrate the orthodontic appliance in situ on thetarget on the tooth model in isometric and cross-sectional view,respectively.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, a first embodiment of the present inventioncomprises a physical model of a tooth arch, generally designated withnumeral 100, comprising a plurality of dental appliance targets 50, alsoreferred to interchangeably herein as targets 50.

In this embodiment, the model 100 is a physical replica, made from asuitable material as is known in the art, representing the real tootharch of a patient regarding which it is desired to provide anorthodontic treatment to at least some of the teeth therein. Inalternative variations of this embodiment, the model may instead be aphysical replica of part of an arch, for example representing a numberof teeth or even representing one tooth of the dentition of the patient.

One or more than one target 50 is provided on the representation of arespective tooth model 110 in the model 100, each at a position relativeto the dental surfaces of the respective tooth model 110 that isconsidered to provide the required orthodontic treatment for the patientwhen the respective orthodontic appliance 90 is placed on thecorresponding position real dental surface of the real respective tooth10 of the patient (FIGS. 1 a, 1 b). It is also to be noted that themodel dental surfaces of the physical model referred to herein areexternal model surfaces that correspond only to the respective realdental surfaces of the real teeth, and thus do not include recesses,indentations or other modifications formed in the model and thatpenetrate the original dental surface of the model, wherein suchrecesses, indentations or other modifications do not have a physicalcounterpart in the real dental surfaces.

Each target 50 is configured for facilitating placement of therespective orthodontic appliance 90 on the model 100, by providingvisual clues and/or mechanical stops, in particular recessed mechanicalstops, for aligning the orthodontic appliance 90 accurately on therespective tooth surface.

Once the orthodontic appliances 90 are affixed on the model 100 at thedesired positions over the respective tooth representations 110, atransfer tray 200 is provided to fit over the model 100. The insideshape of each of the cavities 220 of the tray 200 is formed to besubstantially complementary to the external shape of the particularmodel tooth of the model 100 that is received therein, in particular thelingual and buccal/labial surfaces of the model teeth. The tray 200 isalso designed to embed or fix the orthodontic appliances 90 into thetray material at their correct positions relative thereto (FIG. 1 a),and when fixed thus, the tray 200, together with the orthodonticappliances 90 can then be removed from the model 100 and transferred tothe real arch of the patient to enable fixation of the orthodonticappliances 90 to the real teeth in an indirect bonding procedure, afterwhich the tray 200 is removed (FIG. 1 b), as is known per se in the art.

Thus, the targets 50 are configured for enabling each of the orthodonticappliances 90, for example brackets, to be properly positioned withrespect to the respective teeth models 110 that they are to betemporarily bonded to, and at least serve as a navigational andpositional guide for the placement of the orthodontic appliances 90 ontothe desired positions on model 100.

Referring to FIGS. 2 a to 2 f, in one embodiment, the target 50 for arespective tooth model 110 is in the form of a recessed mechanical stop,and comprises a cavity or recess 60 indented or otherwise projectinginto the surface 115 of the tooth model 110, and appropriately shaped toenable an orthodontic appliance 90 to be mechanically received therein.In particular, the recess 60 is defined by a rectangular planform withfour inward facing edges 62 that are complementary to and correspond tothe four outer edges 92 of the base element 94 of an orthodonticappliance 90, and which circumscribe a base 63 of the recess 60. Theedges 62 of the recess 60 have a plan shape substantially complementaryto the plan shape of the part of the appliance 90 that is to be inabutting contact with the real tooth, and thus define the location ofthe edges 92 of the base 93 of orthodontic appliance 90, which can thenbe placed in the desired location on the respective tooth model 110 bysimply inserting the base 93 in the recess 60, for later transfer to thereal tooth via the transfer tray 200. Typically, the tooth model 110 issolid or at least has a thickness in the region of the recess 60 suchthat the abutment surface 93 a (FIG. 2 f) of the base 93 can be inabutment with the model material, directly or indirectly via a bufferlayer.

In the embodiment of FIGS. 2 a to 2 f, the shape of abutment surface 93a (FIG. 2 f) of the base 93 essentially follows the contour of theoriginal tooth surface portion 113 of the tooth model 110 that is nowmissing on account of the recess 60 (FIG. 2 b), but is generallyuniformly linearly displaced inwardly into the tooth model 110 withrespect to the contour of the missing tooth surface portion 113, forexample in an orthogonal direction with respect thereto. In this manner,when an initially flowable buffer material layer 65, such as anadhesive, is placed between the appliance base 93 and the recess base63, once the layer 65 sets and solidifies, the abutment surface 66 ofthe layer 65 has a shape complementary to that of recess base 63, andthus also of the original tooth surface 113 “above” the recess base 63.This enables the orthodontic appliance 90, together with the shapedlayer 65, to sit in close fitting abutment over the tooth surface of therespective real tooth 10 after the orthodontic appliance 90 istransferred thereto via the tray 200.

Thus, the recess 60 has a nominally uniform depth with respect to themodel tooth surface which can be of the same order as the thickness ofthe base 94, for example, or alternatively more, or alternatively less,but sufficient to enable the orthodontic appliance 90 to be positivelylocated in the recess by the user, without the need for special toolsother than optionally a holder for manipulating the orthodonticappliance 90 into engagement with the recess 60.

The recess 60 may be formed on the buccal/labial side, or on the lingualside, or one recess 60 may be provided at each of both sides of thetooth 110 of model 100, as required. In particular, and referring toFIGS. 2 a and 2 c, the recess 60 is of a shape and size substantiallycomplementary to the shape and size of the desired respectiveorthodontic appliance 90 that is to be fitted there into via base 93.

In operation, the appliance 90 is manually maneuvered into place by theuser, and fixed in place in the recess 60, for example by means of aweak adhesive, and the transfer tray 200 is formed over the model 100including the appliance 90. Alternatively, in some cases the orthodonticappliance 90 may have an interference fit with respect to the recess 60,and thus is held in place therein without the need for use of anadhesive. In any case, once the orthodontic appliance 90 is engaged inthe recess 60 and the tray formed over the model 100 and the orthodonticappliance 90, the tray 200 together with the orthodontic appliance 90 insitu is removed from the model 100, and transferred to the intra-oralcavity of the patient, such that the orthodontic appliance 90 is bondedto the respective real tooth of the patient. The above procedure is ofcourse applicable to one or to a plurality of orthodontic appliances 90that are transferred via the tray 200.

In this embodiment, the appliance 90 sits substantially on the samelocation and orientation along the surface of the real tooth as in thetooth model 110, but on the surface of the real tooth rather than belowthe tooth surface, in contrast with the position of the orthodonticappliance 90 with respect to the model tooth 110, in which theorthodontic appliance 90 was accommodated in recess 60, below the modeltooth surface. Since the orthodontic appliance 90 is fully constrainedin all six degrees of freedom by the tray 200, the orthodontic appliance90 is made to abut the respective tooth by making use of the elasticityof the tray and manually pressing the orthodontic appliance 90 towardsthe respective tooth. The elasticity of the tray 200 also assists inenabling the orthodontic appliances 90 to be extracted from theirrespective recesses 60 in the model 100 when removing the tray 200 fromthe model 100.

In an alternative variation of this embodiment, and referring to FIGS. 2e and 2 f in particular, the orthodontic appliance 90 may be fitted witha buffer layer 91 that is designed to have the same thickness as thedepth of recess 60. Thus, when the orthodontic appliance 90 with thebuffer layer 91 is implanted in the recess 60, the full height of theorthodontic appliance 90 stands above the surface of the model tooth110. For example, the buffer layer 91 may comprise a piece of sheetmaterial of the desired thickness, and cut to have the same planform asthe base 93, or such as to have a planform that is enclosed within theedges 92. When the transfer tray 200 is placed over the model 100 andthe orthodontic appliance 90, this is removed from the respective toothmodel 110, and the buffer layer 91 may be removed from the appliance 90at the same time or at a later time prior to attachment of the applianceto the real tooth 10. Thus, when the transfer tray 200 places theorthodontic appliance 90 on the real tooth 10, the orthodontic appliance90 is at the same position in all degrees of freedom with respect to thereal tooth 10 as it was with respect to the tooth model 110.

In yet another variation of the embodiment of FIG. 2 e, the buffer layer91 may be made of a magnetized or magnetizable material, and may bemounted in the recess 60, optionally permanently, for example bybonding. Location and placement of this magnetized buffer layer isfacilitated by having the plan shape of the buffer layer substantiallycomplementary to that of the recess 60, similar to placement of theorthodontic appliance 90 in recess 60 according to the embodiment ofFIGS. 2 a to 2 d, mutatis mutandis. Then, the orthodontic appliance 90,which at least for this case is made from a magnetic or magnetizablematerial or comprises a magnetic or magnetizable material at least atthe base 94 thereof, is located over the magnetized buffer layer 91 bymeans of the magnetic attraction there between. In use, the tray 200 isformed over the orthodontic appliance 90, which is transferred to thereal tooth, as before.

In alternative variations of the embodiment of FIGS. 2 a to 2 f, andreferring to FIGS. 3 a to 3 c for example, the recess base 63 a may beinclined in any suitable manner with respect to the original surfaceprofile 67 of the tooth model 110 directly above the recess 60,according to the desired inclination of the orthodontic appliance 90with respect to the tooth surface. For example, a desired level oftorque and/or tip and/or rotation angles may be provided on the realtooth surface (FIG. 3 c) by suitably varying the depth(s) of one or moreof the edges 62 of the recess 60 (FIGS. 3 a, 3 b), in a suitable mannersuch as to incline the recess base 63 a. Thus, as illustrated in FIGS. 3a to 3 c, the orientation of the appliance 90 with respect to thesurface of the real tooth 10, as symbolized by an imaginary datum line90A orthogonal to the surface, is inclined by an angle a with respect tothe inclination of the appliance with respect to its position on thetooth model 110 (datum line 90B).

In an alternative variation of this embodiment, and referring to FIGS. 4a to 4 f, the target 50 may be in the form of a wedge-shaped recess 160,having three edges 162 in the shape of a U against which the desiredbracket or other orthodontic appliance 90 can be abutted by means ofthree edges 92 thereof to positively fix the position of the orthodonticappliance 90 with respect to the respective tooth model 110. Thus, therecess 160 lacks a fourth recessed edge at the opening 163 a of the U inthe occlusal direction towards the apex 119 of the tooth model 110. Asbest seen in FIG. 4 e, the lack of a recessed edge at opening 163 afacilitates removal of the tray 200 together with the orthodonticappliance 90, as the tray 200 is essentially lifted away from the toothmodel 110 in the direction of the opening, i.e., in the occlusaldirection, and there is no resistance offered by the recess 160 tomovement of the orthodontic appliance 90 in this direction. Whentransferred to the real tooth 10 (FIG. 41), the appliance 90 sitssubstantially on the same location and orientation along the surface ofthe tooth 10 as in the model 110, but in relative terms the appliance isslightly tilted on the surface of the real tooth 10 with respect to itsoriginal position relative to the tooth model 110.

Optionally, and referring to FIG. 4 g, the orthodontic appliance 90 maybe fitted with a buffer layer 291 that is designed to have the samecross-section as that of recess 260, i.e. the wedge-shaped variablethickness as the depth of recess 260, so that when the orthodonticappliance 90 with the buffer layer 291 is implanted in the recess 260,the full height of the orthodontic appliance 90 stands above the surfaceof the model tooth 110. When the transfer tray 200 is placed over theorthodontic appliance 90, this is removed from the model 110, and thebuffer layer 291 is removed at the same time or later. Thus, when thetransfer tray 200 places the orthodontic appliance 90 on the real tooth,the orthodontic appliance 90 is at the same, correct position in alldegrees of freedom, with respect to the real tooth 10 as it was withrespect to the tooth model 110. Otherwise, the embodiment of FIGS. 4 ato 4 g is substantially similar to that of FIGS. 2 a to 2 f and 3 a to 3c, mutatis mutandis.

In an alternative variation of the embodiment of FIGS. 4 a to 4 g, andreferring to FIGS. 5 a to 5 d, the target 50 is also in the form of anopen recess 260, but this is a V-shaped recess having only two adjoiningedges 263 against which the desired bracket or other orthodonticappliance 90 can be abutted to positively fix the position of thebracket with respect to the model 100. In a similar manner to theembodiment of FIGS. 4 a to 4 g, mutatis mutandis, the lack of a recessededge at opening 263 a of the “V” facilitates removal of the tray 200together with the orthodontic appliance 90, as the tray is essentiallylifted away from the tooth model 110 in the direction of the opening,and there is no resistance offered by the recess 260 in this direction.Also similarly, mutatis mutandis, when transferred to the real tooth,the appliance 90 sits substantially on the same location and orientationalong the surface of the real tooth as in the model 110, but in relativeterms the appliance may be slightly tilted on the surface of the realtooth with respect to its position in the model 110, though optionally abuffer layer similar to that of FIG. 4 g, mutatis mutandis, may be usedwith the embodiment of FIGS. 5 a to 5 d to enable the orthodonticappliance 90 to be oriented on the model 110 in the exact manner that itis wished to place the orthodontic appliance on the real tooth.

The targets 50 in the form of recesses 60, 160 or 260 can be formed onthe tooth model 100, for example as follows.

The location and orientation of the targets 50 for each real tooth arefirst identified, according to a set up plan provided by theorthodontist, as the respective locations and orientations appropriatefor bonding or otherwise fixing the brackets or other orthodonticappliances onto the misaligned teeth of the arch such that the teeth maybe aligned in the manner desired in response to the orthodontictreatment.

According to an aspect of the invention, and referring to FIG. 7, a 3Dnumerical model of the teeth of the patient is provided, and thethree-dimensional positions of the brackets or other orthodonticappliances with respect to the 3D numerical model are defined, accordingto method 400.

For example, in step 410, the three dimensional (3D) structure of thepatient's dentition, including the teeth that are required to be movedduring the course of the orthodontic treatment, and preferably the fulldentition of the arch on which these teeth are located, is determined,and provided in digitized form, hereinafter referred to as the initial3D digitized model or virtual model of the dentition, D1. Optionally thethree dimensional (3D) structure of both arches is provided.

The 3D digitized dental model D1 may be obtained in any number of ways.For example, the intra-oral cavity may be scanned or imaged usingtechnology known in the art, including X-rays, CT, MRI, using directcontact methods or using non-contact methods such as for example thosethat employ an optical probe scanner. For example, such a scanner maycomprise a probe for determining three dimensional structure by confocalfocusing of an array of light beams, for example as marketed under thename of iTero or as disclosed in WO 00/08415, the contents of which areincorporated herein in their entirety. Alternatively, the requiredscanning may be accomplished using any suitable scanning apparatus forexample comprising a hand held probe. Optionally, color data of theintraoral cavity may also provided together with the 3D data, and thusthe first virtual model 500 comprises spatial and color information ofthe dental surfaces scanned. Examples of such scanners are disclosed inUS 2006-0001739, and which is assigned to the present Assignee. Thecontents of the aforesaid co-pending application are incorporated hereinby reference in their entirety. Alternatively, an impression (negativecasting) of a patient's teeth is obtained in a manner well known in theart, and this is used for preparing a positive cast suitable forscanning or imaging. Alternatively, the negative casting itself isscanned or imaged. Alternatively, a composite positive-negative modelmay be manufactured and processed to obtain 3D digitized data, forexample as disclosed in U.S. Pat. No. 6,099,314, assigned to the presentAssignee, and the contents of which are incorporated herein in theirentirety. In any case, the 3D virtual model D1 may be associated with acomplete dentition, or with a partial dentition, comprising the teeththat are to be treated.

Providing a digitized data set corresponding to the virtual model D1from such scanning or imaging is also known in the art and will not bedescribed further. The digitized data set of virtual model D1 ismanipulable by means of a computer, and thus allows the next step to beperformed using a suitable computer.

In the next step 420, computer based methods are used for generating theset up, and the virtual model D1 is manipulated to provide a final tootharrangement comprising a final digitized data set corresponding to afinal 3D virtual model D2, in which each virtual tooth is positioned inthe desired position, for example as disclosed in WO 99/34747 or in U.S.Pat. No. 5,975,893, the contents of which are incorporated herein intheir entirety. Essentially, the 3D digitized data corresponding to theindividual teeth of the initial virtual model D1 are separated from oneanother, and the user repositions the 3D individual tooth data for eachtooth based on visual appearance, and/or using rules or algorithms,and/or according to prescriptions provided by the orthodontist, toprovide the final virtual model D2.

In the next step 430, and based on the final data set corresponding tovirtual model D2, brackets or other orthodontic appliances are chosenand “virtually” positioned within the computer environment, i.e. bymeans of the computer, on the aligned teeth virtual model D2, and thecorresponding positions of the brackets or other orthodontic appliancesare then mapped back to the initial virtual model D1 in step 440. Theposition and orientation of the brackets or other orthodontic appliancescan then be incorporated into the initial virtual model D1, and virtualartifacts which correspond to the shape of the recess 60, 160 or 260that is chosen for each particular target 50, collectively referred toherein as target virtual model TVD1, are created in step 450, and may beadded to virtual model D1 to provide modified virtual model D1′ in step460, which includes the original virtual model D1 modified to integrallyinclude the chosen recesses 60, 160 or 260 in the positionscorresponding to the chosen respective orthodontic appliances 90 insteadof the original virtual tooth surfaces at those positions.

In alternative variations of this embodiment, the position andorientation of the brackets or other orthodontic appliances are providedin a different manner—for example manually, or by directly interactingwith model D1 to choose each position and orientation using thepractitioner's skill and experience. The positions and orientations canthen be incorporated into the initial virtual model D1, and virtualartifacts which correspond to the shape of the recess 60, 160 or 260that is chosen for each particular target 50, collectively referred toherein as target virtual model TVD1, are created in step 450, and may beadded to virtual model D1 to provide modified virtual model D1′ in step460.

The physical model is then manufactured in step 470 based on the virtualmodels D1 and TVD1, or based on the virtual model D1, using computercontrolled manufacturing methods.

For example, the model 100 may be manufactured using material removaltechniques, for example CNC machining methods, or other methods, such asfor example rapid prototyping techniques.

Using CNC machining methods, the model 100 may be produced eitherindirectly or directly. Such indirect methods may comprise, e.g.,manufacturing an appropriate female mold using CNC techniques, and thenproducing a model 100 from the mold. The female mold comprises aninternal 3D structure substantially complementary to that defined byvirtual model D1′.

In direct CNC machining methods, a suitable CNC machine may beprogrammed to provide material removal passes over a blank of suitablematerial, based on dataset D1 or D1′, such as to manufacture the model100. For example, the targets 50 may be integrally formed with the model100, wherein the model 100 is manufactured based on virtual model D1′.Alternatively, the targets 50 may be formed as a separate machiningoperation after the model 100 is produced based on virtual model D1,wherein the position and form of the targets 50 is post-machined basedon target virtual model TVD1.

Alternatively, the model 100 may be formed using other techniques suchas for example from an impression of the intra-oral cavity, and thetargets 50 may be subsequently formed on such a physical model using CNCmachining techniques based on target virtual model TVD1. In such a case,the spatial position and orientation of model 100 as a whole must beknown with respect to a machining datum so that CNC machining operationsare applied to the desired parts of the model to form the recesses 60,160 and/or 260. Accordingly, it is possible to set the model 100 on arig or chuck to hold the same in place, and thereafter scanned using asuitable 3D scanner to provide a 3D virtual model, nominally equivalentto model D1, to be followed by machining of the recessed based on targetvirtual model TVD1, which is manipulated to be in registry with thevirtual model of the scanned physical model 100. Alternatively, themodel 100 may be fabricated with indicia that help align the model 100with respect to predetermined datums in the CNC machine, to which thetarget virtual model TVD1 is also referenced.

Alternatively, the model 100 may be fabricated using other methods. Forexample, the model 100 may be fabricated using rapid prototypingtechniques, for example based on a stereolithography machine, such asfor example Model SLA-250/50 available from 3D System, Valencia, Calif.,based on the virtual model D1. A liquid or non-hardened resin ishardened into a 3D form that can be separated from the non-hardenedliquid or resin to form a positive model 100 from the 3D numerical modelD1 thereof. Then, the targets 50 may be formed in the model 100 in asimilar manner to that described above, for example, mutatis mutandis,for example by CNC machining. Alternatively, the model 100 may bemanufactured integrally with the targets 50 using rapid prototypingtechniques in a similar manner to that described herein, mutatismutandis, based on virtual model D1′.

Once the physical tooth model 100 is manufactured, including the targets50, the orthodontic appliances 90 are temporarily affixed to the toothmodels 110 at positions provided by the targets 50, i.e. recesses 60,160 and/or 260, via a weak adhesive, interference fit, and so on,optionally with a buffer layer, as already disclosed herein. The tray200 may then be manufactured for example as in traditional indirectbonding techniques, comprising pressure or vacuum forming a suitablesheet material, such as 0.75 mm thermal forming dental material, overthe model 100 and appliances 90. Suitable thermal forming dentalmaterials may include, for example, biocryl, by Great Lakes OrthodonticsLtd., Tonawanda, N.Y.

In a second embodiment of the invention, and referring to FIGS. 6 a to 6b, the physical model 100′ comprises all the elements and features ofthe first embodiment, as described herein mutatis mutandis, with thefollowing differences. In the second embodiment, the targets 50 areconfigured to provide visual clues on the physical model 100′ whichenable the orthodontic appliances 90 to be located at the desiredlocations over the respective tooth model 110 of model 100 in theabsence of any recessed mechanical structure or stops that areconfigured for defining the location of the appliance 90 by abutmenttherewith.

In the embodiment of FIGS. 6 a and 6 b, having chosen the particularorthodontic appliance 90 having a known shape for the base 94 thereof, anumber of notches 360 are provided on the respective tooth model 110 ofthe model 100. The notches 360 coincide with parts of the periphery 98of the base 94, enabling the base 94 to be visually aligned with thenotches, thereby enabling the orthodontic appliance 90 to be navigatedinto its correct position, although the notches do not mechanically holdthe appliance 90 in place with respect to any degree of freedom. As bestseen in FIG. 6 b, the notches 360 comprise a physical cut or anindentation into the surface of the tooth model 110.

In a variation of this embodiment, and referring to FIG. 6 c, theplurality of notches 360 of FIGS. 6 a and 6 b is replaced with singlenotch 362 that circumscribes the periphery 98 of base 94.

In another variation of this embodiment, and referring to FIG. 6 d, theplurality of notches 360 of FIGS. 6 a and 6 b is replaced, oralternatively supplemented, with targeting marks 364 that help the useralign the periphery 98 of base 94 in the desired location.

In yet another variation of this embodiment, and referring to FIGS. 6 eand 6 f, targeting marks 366 are engraved or otherwise formed on thesurface of the tooth model 110, for example generally aligned in theocclusal direction, and these marks are to be aligned with referencemarks 290 provided on the appliance 90. Thus, and as illustrated in FIG.6 f, when the targeting marks 366 and reference marks 290 are aligned,the appliance 90 is considered to be in the desired location on thetooth model. Of course, the targeting marks may be inclined at any anglewith reference to the occlusal direction, and arranged in any desiredmanner on the tooth model 110, so long as this matched the correspondingmarks on the appliance 90, such that aligning the targeting marks on thetooth model with the marks on the appliance positions the appliance onthe model in a unique and repeatable manner.

As illustrated in FIG. 6 h, the targeting marks 366 may be directlyengraved into the surface of the model 110 to provide an indentation368′, or alternatively, as illustrated in FIG. 6 g, the marks 366 may beformed as protruding structures 367 by removing material in the vicinityof the marks to provide a slight indentation 368 at least partiallysurrounding the protruding structures 367. However, it is to be notedthat the surface of the indentation 368, or of indentation 368′, is notconsidered a “dental surface” per se in the meaning of the presentinvention, as it does not correspond to a real dental surface of thereal teeth.

Alternatively, the position of a datum with respect to each orthodonticappliance 90 may be marked on the respective tooth model 110, forexample as a “+” or “X” symbol or mark, such that the center or otherpart of the mark corresponds to the center or other known locationrelative to the orthodontic appliance 90, respectively, and theorientation of the mark is indicative of the desired orientation of theorthodontic appliance 90, for example. Such a reference datum may bereferred to a bracket centerline, bracket slot or any other convenientreference on the orthodontic appliance 90 by which it is possible toplace the orthodontic appliance 90 in a desired position with someaccuracy.

Thus, according to one aspect of the second embodiment, the targets 50are in the form of a physical marking that is engraved, scratched orotherwise formed as a depression into the surface of the tooth model100.

Alternatively, according to another aspect of the second embodiment,rather than providing a physical mark as an indentation into the surfaceof the physical model, the targets 50 in the second embodiment andvariations thereof may be provided as optical marks, which arecharacterized as having a different color and/or contrast or otheroptical property with respect to the rest of the surface of the physicalmodel 100, in particular the respective tooth model 110 thereof, withoutnecessarily providing a physical mark that is engraved or otherwisephysically projecting into the surface of the tooth model. Thus, suchtargets 50 can be printed, drawn, painted, colored or otherwise providedon the surface of the tooth model 110, similar to the notches and otherphysical markings of the embodiment of FIGS. 6 a to 6 d, mutatismutandis, without the necessity of actually or effectively physicallyremoving material with respect to the dental surfaces of the model 100.

In yet another variation of the second embodiment, the targets 50 areprovided as visual clues that are slightly protruding from the originalsurface of the tooth model 110, though not sufficiently and/or in aconfiguration to provide a mechanical structure or stops that areconfigured for defining the location of the appliance 90 by abutmenttherewith.

The targets 50 in the form of notches 360, 362, 364, 366 etc, orcorresponding optical markings can be provided in a similar manner tothe recesses 60, 160 or 260 of the first embodiment, mutatis mutandis,with some differences, for example as follows.

Referring to FIG. 8, a 3D numerical model of the teeth is provided, andthe three-dimensional positions of the brackets or other orthodonticappliances with respect to the 3D numerical model are defined, and thephysical model according to the second embodiment or variations thereofis manufactured, according to method 500.

Method 500 comprises method steps 510, 520, 530, 540, which aresubstantially identical to method steps 410, 420, 430, 440, respectivelyof method 400 as disclosed herein, mutatis mutandis.

In the next step 550, virtual models of the targets 50 in the form ofthe positions and shapes of the virtual markings arecreated—collectively referred to as TVD2—based on the shapes andlocations of the chosen orthodontic appliances 90.

In step 560, the initial virtual model D1 is updated to incorporate thevirtual models TVD2 to create an updated initial virtual model D1″, inwhich the original virtual model D1 modified to integrally include thechosen markings in the positions corresponding to the chosen respectiveorthodontic appliances 90 instead of the original virtual tooth surfacesat those positions.

In the next step 570, the physical model 100 of the dentition includingthe targets according to the second embodiment or variations thereof ismanufactured using computer controlled manufacturing methods, based onvirtual models D1 and TVD2, or based on virtual model D1″.

Step 570 may be carried out in a number of ways, for example usingmaterial removal techniques, for example CNC machining methods, or othermethods, such as for example rapid prototyping techniques.

Using CNC machining methods, the model 100 may be produced eitherindirectly or directly. Such indirect methods may comprise, e.g.,manufacturing an appropriate female mold using CNC techniques, and thenproducing a model 100 from the mold using casting techniques. The femalemold comprises an internal 3D structure substantially complementary tothat defined by virtual model D1′, in which the locations and form ofthe markings are integrally and complementarily formed in the femalemold as beads or the like, which form the required physical markings inthe form of notches or the like indented into the surface of the castmodel, when the targets 50 are chosen thus.

Alternatively, in direct CNC methods, a suitable CNC machine may beprogrammed to provide material removal passes over a blank of suitablematerial, based on dataset D1 or D1″, such as to manufacture the model100. For example, the targets 50 in the form of the aforesaid physicalmarkings indented into the model may be integrally formed with the model100, wherein the model 100 is manufactured based on virtual model D1″.Alternatively, the targets 50 may be formed as a separated operationafter the model 100 is produced based on virtual model D1, wherein theposition and form of the targets 50 is post-machined based on targetvirtual model TVD2. For example, a sharp tool may be CNC controlled toprovide the physical markings on the model. In the case where at leastsome of the targets 50 are the aforesaid optical markings, a toolcomprising a pen, printer head or the like may be mounted onto a CNCcontrolled machine, and CNC controlled so as to print, draw or paint theoptical markings at the required positions on the model 100.

Alternatively, the model 100 may be formed using other techniques suchas for example from an impression of the intra-oral cavity, and thetargets 50 in the form of physical markings or optical markings may beformed using CNC machining techniques based on target virtual modelTVD2, as disclosed above, mutatis mutandis. In such a case, the spatialposition and orientation of model 100 as a whole must be known withrespect to a machining datum so that marking operations are applied tothe desired parts of the model to form the physical or optical markings.Accordingly, it is possible to set the model 100 on a rig or chuck tohold the same in place, and thereafter scanned using a suitable 3Dscanner to provide a virtual model of the physical model, to be followedby creation of the physical or optical markings based on target virtualmodel TVD2, which is manipulated to be in registry with the virtualmodel of the scanned physical model 100. Alternatively, the model 100may be fabricated with indicia that help align the physical model 100with respect to predetermined datums in the CNC machine, to which thetarget virtual model TVD2 is also referenced.

Alternatively, the model 100 is fabricated using other methods. Forexample, the model 100 may be fabricated using rapid prototypingtechniques, for example based on a stereolithography machine, such asfor example Model SLA-250/50 available from 3D System, Valencia, Calif.,based on the virtual model D1. A liquid or non-hardened resin ishardened into a 3D form that can be separated from the non-hardenedliquid or resin to form a positive model 100 from the 3D numerical modelD1 thereof. Then, the targets 50 in the form of physical markings oroptical markings may be formed in the model 100 in a similar manner tothat described above, for example, mutatis mutandis, for example by CNCcontrol.

Alternatively, the model 100 may be manufactured integrally with thetargets 50 using rapid prototyping techniques based on virtual modelD1″, in a similar manner to that described above for virtual model D1′,mutatis mutandis. Where the targets 50 comprise physical markings, therapid prototyping method automatically creates the physical markings byproviding an effective absence of material at the respective locationsof the markings. Additionally or alternatively, where the targets 50comprise optical markings, the stereolithography machine may beprogrammed to provide at the locations of the markings, resin having adifferent optical property to that of the resin used for rest of themodel 100, at least when the resin hardens, so that the optical markingsare visually marked on the model as lines or symbols and so on having adifferent optical property or characteristic—color, contrast, etc—to therest of the model 100.

Once the model 100 is finished with the targets 50 in the form of thephysical markings and/or the optical markings, the orthodonticappliances 90 are placed at the correct positions on model 100 as guidedby the markings, and the transfer tray 200 may then be manufactured, forexample as in traditional indirect bonding techniques, comprisingpressure or vacuum forming a suitable sheet material, such as 0.75 mmthermal forming dental material. Suitable materials include, forexample, biocryl, by Great Lakes Orthodontics Ltd., Tonawanda, N.Y.

Both for the first and second embodiments, the targets 50 may be createdas a separate CNC controlled machining operation of the physical model100, using any suitable tooth, such as for example a sharp or heatedcutting tool, a laser or a power tool, marking tool, printing tool, andso on, as appropriate.

Thus, the targets 50 thus provided enable locations of orthodonticappliances 90 to be targeted, and for the orthodontic appliances 90 tobe navigated, homed onto and placed at the desired areas of the physicaltooth model 100, and thus also to be placed onto the desired areas ofthe patient's teeth by means of the transfer tray 200. Optionally, themodel 100 may be suitably marked in the vicinity of each target 50 withan identifying mark, symbol or alphanumeric character, for example, thatidentifies the particular type of orthodontic appliance 90 that issupposed to be targeted onto and bonded to the particular tooth model110 of the model 100 via that target 50. Such an identifier may beprinted, etched or in any other manner provided on the model 100.

Thus, a suitable marking implement such as a pen, pencil, printing pador the like, for example, may be used to mark the area, in ink forexample, this mark delineating the position required for the orthodonticappliance 90, for each tooth.

The present invention may also be used for providing remedial assistanceduring an orthodontic procedure that is already under way. Suchassistance may arise when a bracket or other orthodontic appliance fallsoff a tooth during the course of an orthodontic treatment, for example.Relative to the corresponding tooth, a particular bracket remains in thesame position during the full duration of the orthodontic treatment.There are at least two ways of re-installing the missing bracket.According to one method, the original tooth model 100 may be used againto place the orthodontic appliance 90 on the particular tooth model 100corresponding to the real tooth that is missing the orthodonticappliance 90. Then, a transfer tray for that tooth only is formed overthe respective tooth model 110 and orthodontic appliance 90, and theorthodontic appliance 90 is transferred to the real tooth via indirectbonding using the single tooth transfer tray. Thus, even if the toothhas moved significantly since the orthodontic treatment started, sincethe relative position of the orthodontic appliance 90 with respect tothe respective tooth is unchanged, the single tooth transfer trayprovides an effective solution.

According to another embodiment of the method, an intermediate virtualmodel of the dentition can be created, in a similar manner to model 100,mutatis mutandis, taking into account the current positions of the teethat the intermediate point of the orthodontic treatment. Then, thevirtual model corresponding to the target 50 of the particular tooth,for example part of TVD1 or of TVD2, is incorporated into thisintermediate virtual model, and a corresponding intermediate physicalmodel can be manufactured together with the target 50 on the aforesaidtooth model 110. The orthodontic appliance 90 is then placed on theparticular tooth model 110 corresponding to the real tooth that ismissing the orthodontic appliance 90 using the respective target 50.Then, a transfer tray for the full model 100 is made, affixing theretoorthodontic appliance 90, which is transferred to the real tooth viaindirect bonding using the transfer tray.

Thus, it may be desired to change the relative position of theorthodontic appliance 90 with respect to the respective tooth, and thusthe procedure may be used for providing remedial assistance, or foradjusting an orthodontic treatment by changing the position of thebracket during treatment.

In another variation of the second embodiment, the optical markings arein the form of a transfer patch of a suitable material that istransferred to the respective tooth model. The transfer patch maycomprise an adhesive label, for example, that is transferred to thetooth model 110. The adhesive label may be, for example, in the shape ofthe periphery of the required orthodontic appliance 90, so that theorthodontic appliance 90 may be fitted in the open area in the patchafter the patch is adhered to the tooth model.

Alternatively, the patch may cover part or all of the target area, andthe orthodontic appliance 90 is fitted onto the patch. The adhesivepatch may comprise a chemical or light-cured adhesive, which sets whenthe patch has been properly seated and aligned on the tooth model 110.Optionally, the patch may comprise adhesive on both sides thereof,enabling the patch to first bond onto the tooth model 110, and thenallow the orthodontic appliance 90 to be bonded to the patch.Accordingly, it may be convenient to have different adhesives for eachof the sides of the patch, and such that each adhesive may beselectively activated independently of the other. For example, theadhesives may be light-curing adhesives, each of which cures at adifferent wavelength. This facilitates the procedure of bonding thepatch to the tooth model first, and then allowing the orthodonticappliance 90 to be bonded to the patch. Optionally, the patch may be inthe form or shape of the bracket, or in any other suitable shape such asto guide the bracket to the required alignment with respect thereto andthus the tooth model.

Once the shape and dimensions of the patch, and their relationship tothe position and orientation of the respective orthodontic appliance 90on the respective tooth model 110, a suitable robot or robotic arm maybe suitably programmed, based on the aforementioned virtual models ofthe intraoral cavity and of the targets, to place the patch at thedesired location over the model 110.

Thus, the physical or optical markings according to the secondembodiment provide sufficient targeting information for each orthodonticappliance 90, which may be positioned and bonded onto the appropriatepart of the tooth model 110 by placing and aligning the orthodonticappliance 90 in registry with the corresponding mark.

The second embodiment also allows the choice of actual bracket to bedeferred if desired or necessary, for example due to logistical problemsin obtaining specific types of brackets. Since the positional datarequired for the orthodontic appliance 90 is marked on the model 100, itis possible to target any orthodontic appliance 90 to a particulartarget 50, so long as the orthodontic appliance 90 comprises suitabledatums compatible with the marking criteria used for the marking, forexample centerline and slot location datums.

In a third embodiment of the invention, the physical model 100 comprisesthe elements and features of the first and second embodiments, asdescribed herein, mutatis mutandis, in which at least one target 50 isconfigured to provide visual clues which enable the orthodonticappliances 90 to be located at the desired locations over the respectivetooth model 110″ of model 100″, and also provides at least onemechanical stop to define the location with respect to at least one axisor degree of freedom by abutment therewith. Thus referring to FIGS. 9 ato 9 d, the target 50 according to the third embodiment comprises aledge-shaped recess 600 formed into the material of the tooth model 110,comprising a shoulder 620 and a base 610. The shoulder 620 and baseprovide abutments for an edge 92 the underside, respectively, of thebase element 94 of an orthodontic appliance 90. In this embodiment, theorthodontic appliance 90 can slide in the direction marked 625 along theedge between the shoulder 620 and base 610, and the desired position ofthe orthodontic appliance 90 along this direction is provided by opticalmarks, similar to those of the second embodiment, for example aperipheral mark 630 corresponding to the perimeter of the base 94,and/or datum marks 640 corresponding to the mid-point and/or corners ofthe side 92 that is in abutment with the shoulder 620. The model 100comprising recess 600 can be manufactured using a combination oftechniques already described for the first and second embodiments,mutatis mutandis, and where the recess 600 is provided as apost-machining operation on a prepared model 100, such a post-machiningoperation is relatively simple, as it may comprise effectively cutting aslice with a wedge-shaped cross-section off from the respective toothmodel.

In a variation of the third embodiment, and referring to FIGS. 10 a to10 d, recess 700 comprises all the elements and features of recess 600of the embodiment of FIGS. 9 a to 9 d, with the following differences.In the embodiment of FIGS. 10 a to 10 d, the recess 700 has a shoulder720 and base 710, rather than providing visual or physical clues foraligning the orthodontic appliance 90 along direction 625, a mechanicalstop 750 is provided, protruding from the base 710, and an edge 92 aadjacent to edge 92 is abutted onto the stop 750, thereby constrainingthe orthodontic appliance 90 onto the tooth model 110 in all degrees offreedom. It is to be noted that in this embodiment, stop 750 has height,width and depths dimensions that are within the envelope defined by theimaginary surface 117 of the tooth model 110 that was removed to formthe recess base 710 and shoulder 720. Thus, for example, the stop 750may be manufactured in a machine removal operation while making therecess 700. Furthermore, it is also to be noted that the surface of therecess base 710 is not considered a “dental surface” per se in themeaning of the present invention, as it does not correspond to a realdental surface of the real teeth.

In a variation of the embodiment of FIGS. 10 a to 10 d, the stop 750 maycomprise a separate component that is mounted in place on base 710 afterthis is cut out or otherwise formed on the tooth model 110. The stop 750is thus manufactured separately to the model 100. When making the recess700, a suitable hole (not shown) may be drilled or otherwise formed onbase 710, and the stop 750 comprises a projection to enable the stop 750to be positioned accurately on the base 710.

In yet other embodiments of the invention, the model 100 may compriseany combination and permutation of targets 50 according to the firstembodiment, and/of the targets according to the second embodiment,and/or the targets according to the third embodiment, mutatis mutandis.

Optionally, the model 100 according to any of the embodiments orvariations thereof, may be fabricated at one location, and thentransported to another location where the targets 50 are formed.Alternatively, the model 100 including targets 50 may be fabricated at asingle location. Further optionally, placement of the orthodonticappliances 90 on the model 100, and/or formation of the tray 200, may beperformed at the same location, or at a different location to that usedfor manufacturing the model 100 and/or the targets 50.

For at least the embodiments or variations thereof disclosed herein, itis possible optionally and additionally to mark the physical model withuseful information including, for example, at least one of: the name ofthe patient; the name of the orthodontist; the name of the dental labthat manufactured the tray; the date of manufacture; the model, type,serial numbers, or other identifying references for the brackets; and soon.

In the method claims that follow, alphanumeric characters and Romannumerals used to designate claim steps are provided for convenience onlyand do not imply any particular order of performing the steps.

Finally, it should be noted that the word “comprising” as usedthroughout the appended claims is to be interpreted to mean “includingbut not limited to”.

While there has been shown and disclosed example embodiments inaccordance with the invention, it will be appreciated that many changesmay be made therein without departing from the spirit of the invention.

What is claimed is:
 1. A dental model for facilitating placement of anorthodontic appliance at a desired location, the model comprising: apositive physical model of at least a portion of a patient's dentition,the positive physical model comprising at least one target, the at leastone target comprising a recessed mechanical stop shaped to receive atleast a portion of the orthodontic appliance and constrain movementthereof in order to facilitate the placement of the orthodonticappliance at the desired location on the positive physical model.
 2. Thedental model of claim 1, wherein the positive physical model comprises amodel dental surface corresponding to a real dental surface of thepatient's dentition.
 3. The dental model of claim 2, wherein therecessed mechanical stop projects into the model dental surface.
 4. Thedental model of claim 1, wherein the recessed mechanical stop is shapedto receive a perimeter edge of the orthodontic appliance.
 5. The dentalmodel of claim 1, wherein the recessed mechanical stop comprises atleast one recess edge to which at least one perimeter edge of theorthodontic appliance is abutted to constrain the movement of theorthodontic appliance.
 6. The dental model of claim 1, wherein the atleast one target further comprises one or more markings providing visualtargeting information to facilitate the placement of the orthodonticappliance at the desired location on the positive physical model.
 7. Amethod for manufacturing a dental model for facilitating placement of anorthodontic appliance at a desired location, the method comprising:forming a positive physical model of at least a portion of the patient'sdentition; and forming at least one target in the positive physicalmodel, the at least one target comprising a recessed mechanical stopshaped to receive at least a portion of the orthodontic appliance andconstrain movement thereof in order to facilitate the placement of theorthodontic appliance at the desired location on the positive physicalmodel.
 8. The method of claim 7, further comprising positioning theorthodontic appliance at the desired location on the positive physicalmodel using the at least one target.
 9. The method of claim 8, furthercomprising: positioning a transfer tray over the positive physical modelso as to embed the orthodontic appliance into the transfer tray;removing the transfer tray and the orthodontic appliance embeddedtherewithin from the positive physical model; and positioning thetransfer tray over the patient's dentition so as to transfer theorthodontic appliance to the patient's dentition at a desired locationcorresponding to the desired location on the positive physical model.10. The method of claim 7, wherein the orthodontic appliance comprises abuffer layer and the recessed mechanical stop is shaped to receive thebuffer layer.
 11. The method of claim 10, wherein the orthodonticappliance comprises an appliance base and the buffer layer is removablyattached to the appliance base.
 12. A system for manufacturing a dentalmodel for facilitating placement of an orthodontic appliance at adesired location, the system comprising: a computer controlledmanufacturing center configured to, form a positive physical model of atleast a portion of the patient's dentition, and form at least one targetin the positive physical model, the at least one target comprising arecessed mechanical stop shaped to receive at least a portion of theorthodontic appliance and constrain movement thereof in order tofacilitate the placement of the orthodontic appliance at the desiredlocation on the positive physical model.
 13. The system of claim 12,wherein the computer controlled manufacturing center is configured toform the positive physical model and the at least one target in thepositive physical model using at least one of a CNC machining process ora rapid prototyping process.
 14. The system of claim 12, wherein thecomputer controlled manufacturing center is configured to form the atleast one target in the positive physical model concurrently whileforming the positive physical model.
 15. The system of claim 12, whereinthe computer controlled manufacturing center is configured to form theat least one target in the positive physical model after forming thepositive physical model.
 16. The system of claim 12, wherein thecomputer controlled manufacturing center is configured to form thepositive physical model and the at least one target in the positivephysical model based on one or more virtual models of the positivephysical model and the at least one target.